package demo;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 *这个类用来对user表进行增删改查操作
 */
public class UserMapper {
    public int insert (User user){
        try ( Connection connection = DBUtil.getConnection();){
           String sql = "INSERT INTO user(username,password,nickname,age) " +
                        "Values(?,?,?,?)";
            PreparedStatement ps = connection.prepareStatement(sql);
            ps.setString(1,user.getUsername());
            ps.setString(2, user.getPassword());
            ps.setString(3, user.getNickname());
            ps.setInt(4,user.getAge());
            return ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return 0;
    }

    /**
     * 根据用户名查询数据，如果用户不存在则返回null
     * @param username
     * @return
     */
    public User selectByUsername(String username){
        try (Connection connection = DBUtil.getConnection();){
            String sql = "SELECT id,username,password,nickname,age " +
                          "FROM user " +
                          "WHERE username=?";
            PreparedStatement ps = connection.prepareStatement(sql);
            ps.setString(1, username);
            ResultSet rs = ps.executeQuery();
            if(rs.next()){
                User user = new User();
                user.setId(rs.getInt("id"));
                user.setUsername(rs.getString("username"));
                user.setPassword(rs.getString("password"));
                user.setNickname(rs.getString("nickname"));
                user.setAge(rs.getInt("age"));
                return user;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 修改用户信息
     * 根据传入的user对象中的用户名，修改该用户的密码
     * @param user
     * @return
     */
  public int update(User user){
      try (Connection connection = DBUtil.getConnection();){
          String sql = "UPDATE user " +
                        "SET password = ?,nickname = ?,age = ? " +
                        "WHERE username  = ?";
          PreparedStatement ps = connection.prepareStatement(sql);
          ps.setString(1, user.getPassword());
          ps.setString(2, user.getNickname());
          ps.setInt(3,user.getAge());
          ps.setString(4,user.getUsername());
          return ps.executeUpdate();
      } catch (SQLException e) {
          e.printStackTrace();
      }
      return 0;
  }

    /**
     * 查询所有用户信息
     * 在User表中每一条记录都可以用一个User对象表示
     * 那么所有数据就可以以若干个
     * @return
     */
  public List<User> sleletAll(){
      List<User> users = new ArrayList<>();
      try(Connection connection = DBUtil.getConnection();) {
          String sql = "SELECT id,username,password,nickname,age " +
                        "FROM user";

          Statement statement = connection.createStatement();
          ResultSet rs = statement.executeQuery(sql);
          while (rs.next()){
              User user = new User();
              user.setId(rs.getInt("id"));
              user.setUsername(rs.getString("username"));
              user.setPassword(rs.getString("password"));
              user.setNickname(rs.getString("nickname"));
              user.setAge(rs.getInt("age"));
              users.add(user);
          }
      } catch (SQLException e) {
          e.printStackTrace();
      }
      return users;
  }
}
